This invention relates in general to driveshaft assemblies for transferring rotational power from an engine/transmission assembly to an axle assembly in a vehicle drive train. In particular, this invention relates to an improved structure for a slip yoke assembly adapted for use in such a vehicular driveshaft assembly, wherein the slip yoke assembly including a sealing and positioning plug. This invention also relates to a method for installing the slip yoke assembly.
In most land vehicles in use today, a driveshaft assembly is provided for transmitting rotational power from an output shaft of a transmission to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a typical driveshaft assembly is connected between the transmission output shaft and the axle assembly input shaft. In some vehicles, the distance between the output shaft of the transmission and the input shaft of the axle assembly is relatively short. In these vehicles, the driveshaft assembly can include a single, elongated driveshaft tube. In other vehicles, the distance between the output shaft of the transmission and the input shaft of the axle assembly is relatively long, making the use of a single driveshaft tube impractical. In these vehicles, the driveshaft assembly can include a driveshaft tube, together with one or more coupling shafts. Multiple piece driveshaft assemblies of this general type have interior portions that are usually supported for rotation by one or more intermediate resilient support structures, which are generally referred to as center bearing assemblies.
The ends of the driveshaft assembly are connected to the output shaft of the transmission and the input shaft of the axle assembly by respective universal joints. Such universal joints are well known in the art and provide a rotational driving connection therebetween, while accommodating a limited amount of angular misalignment between the rotational axes of the various shafts. Not only must the driveshaft assembly accommodate a limited amount of angular misalignment, but it must also typically accommodate a limited amount of axial movement between the transmission output shaft and the axle assembly input shaft. A small amount of such relative axial movement frequently occurs when the vehicle is operated. To address this, it is known to provide one or more slip yokes in the driveshaft assembly.
In many instances, a slip yoke is provided between the output shaft of the transmission and the universal joint connected to the adjacent end of the driveshaft assembly. The transmission output shaft is typically formed as a generally cylindrical member including an end portion having a male splined outer surface. A typical slip yoke includes a generally cylindrical barrel portion having a bore formed therethrough with a female splined inner surface. The female splined inner surface of the barrel portion of the slip yoke cooperates with the male splined outer surface of the transmission output shaft to provide a rotatable driving connection between the slip yoke and the transmission output shaft, while allowing a limited amount of relative axial movement therebetween. The slip yoke further includes a lug portion comprising a pair of lug ears which extend from the end of the barrel portion. The lug ears have aligned openings formed therethrough that are adapted to receive portions of the universal joint therein. A welch plug or other sealing device is provided to close the end of the bore adjacent to the lug portion. The welch plug prevents the entry of dirt, water, and other contaminants into the region where the splined members engage one another, and further prevents transmission fluid from leaking out through the slip yoke.
In practice, the driveshaft assembly, including the driveshaft tube, the coupling tubes and center bearings (if necessary), the universal joints, and the slip yoke are often pre-assembled as a unit, generally referred to as a coupling shaft assembly, then shipped to another location for installation on the vehicle. To perform such installation, the slip yoke is connected to the output shaft of the transmission by sliding the barrel portion of the slip yoke onto the output shaft of the transmission such that the respective splines formed thereon cooperate with one another. When the slip yoke is properly positioned relative to the transmission output shaft, the center bearing assembly is fastened to the frame of the vehicle to fix the position of the driveshaft assembly.
During the installation process, it is important to properly position the slip yoke relative to the transmission output shaft. If the lug portion of the slip yoke is positioned too close to an external booted seal that is often mounted on the transmission housing, it may cause damage to the seal during operation of the vehicle. The proper positioning of the coupling shaft assembly is also important for the positioning of the remaining drive line components.
In the past, different methods have been used to properly position the slip yoke relative to the transmission output shaft. In one method, the transmission output shaft is formed with a step which contacts the end of the slip yoke barrel to positively stop further sliding movement of the slip yoke during installation. Unfortunately, this method requires that the slip yoke be formed having a relatively long barrel, undesirably increasing the weight and cost thereof. In another method, a groove is machined in the splined inner surface of the slip yoke bore, and a snap ring is installed in the groove. The snap ring contacts the end of the transmission output shaft to positively stop further sliding movement of the slip yoke. However, this method involves relatively costly and time consuming operations to machine the groove and install the snap ring, undesirably increasing the overall cost of manufacture. In yet another method, an instrument or fixture is used to locate the center bearing assembly relative to the vehicle frame. This method is also relatively time-consuming, and further is subject to operator error. Thus, it would be desirable to provide an improved structure for a slip yoke assembly that provides a positive stop for properly positioning the slip yoke relative to the transmission output shaft during assembly into a vehicle.
This invention relates to an improved structure for a slip yoke assembly adapted for use in a vehicular driveshaft assembly. The slip yoke assembly includes a slip yoke having a positioning plug provided therein. The slip yoke includes a barrel portion having a first end and a second end. A pair of lugs extends from the first end of the barrel portion. The barrel portion has a bore extending from the first end to the second end defining a female splined inner surface. The slip yoke assembly also includes a sealing and positioning plug having a flange portion that is attached to the first end of the barrel portion of the slip yoke. The plug also has a body portion that extends from the flange portion a predetermined distance inwardly into the bore. A shaft, such as a transmission output shaft, has an end portion that is disposed inside the bore of the slip yoke. The end portion includes an end which abuts the body portion of the plug. The end portion of the shaft has a male splined outer surface that cooperates with the female splined inner surface of the slip yoke bore to provide a rotatable connection between the shaft and the slip yoke, while allowing a limited amount of relative axial movement therebetween. The invention also relates to a sealing and positioning plug. The plug includes a flange portion having a chamfered outer edge. The flange portion defines a plane. The plug also includes a body portion that extends from the flange portion. The body portion extends a predetermined distance in a direction generally perpendicular to the plane of the flange portion. The invention further relates to a method of attaching a sealing and positioning plug to a slip yoke. A plug is provided including a flange portion and a body portion extending from the flange portion. A slip yoke is provided including a barrel portion having a first end and a second end, and a lug portion extending from the first end of the barrel portion. The barrel portion has a bore extending from the first end to the second end, the bore having a splined inner surface. The flange portion of the plug is positioned on the first end of the barrel portion of the slip yoke, and the body portion of the plug is positioned inside the bore. The material of the slip yoke is deformed over the flange portion of the plug to attach the plug to the slip yoke. The invention also relates to a method of installing a slip yoke on a shaft. A slip yoke is provided including a barrel portion having a first end and a second end, and a lug portion extending from the first end of the barrel portion. The barrel portion has a bore extending from the first end to the second end, the bore having a splined inner surface. A sealing and positioning plug is attached to the slip yoke. The plug includes a flange portion which is attached to the first end of the barrel portion of the slip yoke. The plug also includes a body portion which extends from the flange portion a predetermined distance into the bore. A shaft is provided having an end portion with a splined outer surface, the end portion including an end. The slip yoke is installed by telescopically inserting the barrel portion of the slip yoke about the end portion of the shaft until the end of the shaft abuts the body portion of the plug to provide a positive stop. The splined outer surface of the shaft cooperates with the splined inner surface of the slip yoke bore to provide a rotatable connection between the shaft and the slip yoke while allowing a limited amount of relative axial movement therebetween.
Various advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.